Those look very nice actually! I used to make my own...back when we were warping the stock iso blocks and nobody seemed to notice or acknowledge the problem...anyway, it was driving me nuts so I made my own out of aluminum and made them water-cooled...exact same principal as yours but mine weren't as nice!
A lot of guys were saying these would be a problem cause they could heat up when taking engine in while hot and could cause vapor lock in the carb if it warmed up too much because of the heat transferred trough the alum block as it sat there with hot engine... long story short, with good gaskets I never had an issue with them and never warped another block! lol
Today though with the thick teflon gaskets, this really has become a non-issue. I'm just not sure anymore if water-cooling is worth it...but I think it may be still somewhat good for us northern guys where the water temp is usually WAY below the air temp in the summer time.